Spatial coding of semantic information: knowledge of country and city names depends on their geographical proximity

We report the case of a patient, A.Z., with a refractory disorder of semantic processing. Using a number of spoken word-written word matching paradigms, her comprehension of the broad proper nouns category of place names was investigated. In addition to being sensitive to temporal factors, A.Z.'s ability to identify country or city names accurately was significantly worse when selecting a target from an array of geographically close rather than distant places. The influence of geographical proximity and location was observed even when identifying proximal and distal English towns, but not with less well-known American states. These close and distant effects are attributed to the build-up of refractoriness in representations with shared neural circuitry. Our findings reveal a previously undocumented level of fine-grain organization in this domain of semantic space. It is argued that information about geographical proximity cannot be encoded in purely verbal or visual terms. Consequently, we propose the existence of a separate module of spatially encoded information within conceptual knowledge.